Nintendo's biggest game of 2018 didn't arrive until December, yet it was still one of the best-selling games of the year

Nintendo

• "Super Smash Bros. Ultimate" was Nintendo's biggest game of 2018 by a longshot.
• With "Super Smash Bros. Ultimate," Nintendo took a big risk on a single game - and it paid off tremendously.
• Despite only arriving on December 7, "Super Smash Bros. Ultimate" is the fifth best-selling game of 2018.

Nintendo took a huge risk in 2018 on a single big game - and it paid off handsomely.

On December 7, Nintendo launched "Super Smash Bros. Ultimate" for the Nintendo Switch. In the final three weeks of 2018, Nintendo managed to outsell huge blockbusters like "Assassin's Creed Odyssey," "Far Cry 5," "Battlefield V" and even "FIFA 2019" - all games that launched on a variety of different consoles, whereas "Super Smash Bros. Ultimate" is only available for Nintendo's Switch.

That's according to video game sales data tracking firm The NPD Group, which issued its 2018 video game sales report this week.

Here's what the top 20 looks like for 2018, ranked by dollar sales:

The NPD Group

Nintendo hasn't given out exact sales numbers for "Super Smash Bros. Ultimate" just yet.

"Super Smash Bros. Ultimate" comes in at No. 5 of 20, beating out huge PlayStation 4 exclusives like "God of War" and "Marvel's Spider-Man." Unsurprisingly, it was also the best-selling game of December.

It sold so well, in fact, that it set a sales record; "Super Smash Bros. Ultimate" is the best-selling platform exclusive in its launch month in the history of video game sales data tracking. It replaced 2010's "Halo: Reach" as the previous record-holder.

Wilder still: The data from NPD doesn't include digital sales of the game through Nintendo's eShop. That means that its fifth place spot on the top 20 best sellers list was secured through physical sales alone.

Read more: There's a new 'Super Mario' game for Nintendo's Switch, and it's a modern mash-up of classic Mario

As NPD Group video games industry analyst Mat Piscatella told Business Insider in an email, securing such a high sales spot for the year without including digital sales, "makes the feat all the more impressive."

"Super Smash Bros. Ultimate"

Piranha Plant from the "Super Mario Bros." series is the first fighter being added to the massive roster of characters in "Super Smash Bros. Ultimate."

"Super Smash Bros. Ultimate" will no doubt continue to sell as the months go on.

The series is notorious for having "legs," which means it's expected to maintain a steady beat of sales for years to come as more Switch consoles are sold and owners go looking for games to play. It certainly doesn't hurt that a variety of new fighters are being added to the game in the coming months, and Nintendo recently announced a North American tournament.

For the time being, it's off to a killer start.